KR101703962B1 - Sliding element, in particular piston ring, and combination of a sliding element with mating running element - Google Patents

Abstract

The present invention relates to a sliding element, comprising: a piston ring made of a metal having a coating with a cast iron or a CrN layer extending outwardly from the inside, a layer Me (C _x N _y ) and a DLC layer, A metal-free DLC layer or a metal-containing substructure and a metal-free DLC upper layer. The present invention relates to a combination of such a sliding element and a relative operating element.

Description

A sliding element, in particular a piston ring, and a combination of a sliding element and a relative operating element,

The invention relates to a sliding element, in particular a piston ring with a coating, and a combination of a sliding element and a mating running element.

The sliding element in contact with the counterpart actuating element is applied in various technical fields. The combination of a piston ring and a cylinder liner can be considered as a typical example. If the cylinders or cylinder liners are made of, for example, aluminum-silicon alloys, their value has been demonstrated for wear and friction losses, especially in spark-ignition engines, diamond like carbon (DLC) coating systems. However, the known DLC layer systems have a need for improvement in terms of service life and suitability for use in diesel engines with iron-based cylinder liners or flame-ignition engines with high power superchargers. Due to the extremely high cylinder pressure and especially the combination of direct injection, there is a greater proportion of the mixed friction state. A crucial factor for the improper stability of the DLC coating system for this type of situation is that the layer thickness should generally be considered to be less than 5 [mu] m.

DE 10 2005 063 123 B3 discloses a DLC coated with a run-in layer. With respect to larger layer thicknesses, in particular, PVD coatings of the CrN series with a layer thickness of 10-30 mu m are known. Although these can improve the service life, the friction loss abrasion resistance deteriorates, and in particular, the insufficient lubrication performance and the scratch resistance deteriorate. On the other hand, due to their amorphous structure, the DLC layer system has the advantage of exhibiting an extremely low adhesion tendency to the relative operating elements, since it is chemically substantially inert to the metal surface.

DE 296 05 666 U1 relates to the constituents of the region of the internal combustion engine coated with an amorphous carbon layer having a hardness graded against the layer thickness, which is metal-free.

DE 10 2008 016 864 B3 discloses a piston ring comprising an adhesive layer extending from the inside to the outside, a metal-containing amorphous carbon layer and an amorphous carbon layer not containing a metal.

WO 2009/106201 A1 relates to elements of an internal combustion engine in which a DLC coupling agent layer, a DLC functional layer and DLC run-in layers are present in a substrate.

Finally, WO 2006/125683 A1 discloses a piston ring having a layer with one element from 1VB, VB or V1B groups extending outward from the inside, a diamond-like nanocomposite composition and a DLC layer.

The present invention provides a sliding element, particularly a piston ring, which, when used, for example, in a spark-ignition engine with a diesel engine or a high-power supercharger, together with an iron-based relative operating element, achieves requirements relating to wear and friction losses As a technical problem.

The present invention also discloses an appropriate combination of sliding elements and relative working elements.

The above-mentioned object of the present invention is achieved by the sliding element disclosed in claim 1.

On the one hand, this sliding element is characterized by a combination of a CrN layer and an outer DLC layer. The DLC layer is either a metal-free or metal-containing substructure and a DLC top layer that does not contain a metal. In other words, the DLC layer at least partially contains no metal, and in particular, on the outer surface, a DLC layer that does not contain a metal. Also, according to large scale experiments, the disclosed coatings show particularly good properties when the Me (C _x N _y ) layer is provided as an interlayer between the CrN layer and the DLC layer. Tests using this layered structure indicate that the wear characteristics of the sliding elements, particularly the surfaces of the piston rings, are improved compared to known structures comprising a Cr adhesive layer and a DLC top layer. This can significantly improve durability. The tests also show that the relative functional coefficients can be significantly reduced.

Thus, in general, the disclosed layer structure can provide improved sliding elements. The CrN layer is preferably added to the basic piston material without an adhesive layer, for example by metal deposition or sputtering. However, in special applications, the CrN layer can be added to the base material of the sliding element by the adhesive layer.

For the sake of clarity, it should be noted that Me represents a metal, which may be, for example, tungsten, chromium, titanium or silicon. In addition, carbon and nitrogen can be present in virtually any proportion in the aforementioned layers, and x and y can range from 0 to 99 atomic% (atomic%). Also, particularly in at least some areas, the coating may extend to the transition surface and extend to the surface adjacent to the at least one running surface. This relates, for example, to the running edges of the piston ring.

Preferred improvements are disclosed in other claims.

Values of 1100-1900 HV 0.002 were found to be suitable for the hardness of the CrN layer or substructure. This embodiment can be combined with the hardness of the DLC layer not containing 1700-2900 HV 0.002 metal and / or the hardness of 800-1600 HV 0.002 metal-containing DLC.

In addition, particularly good properties of the DLC-layer, especially the metal-containing and / or metal-free DLC layer, are expected to be obtained if it contains hydrogen.

Preferably, the metal-containing DLC layer may comprise nanocrystalline metal carbide precipitates, such as, for example, WC, CrC, SiC, GeC or TiC.

Favorable properties was confirmed in the entire layer of the thickness of the CrN, 2㎛ up Me (C _x N _y) having a thickness of layers and having a thickness of 1-30㎛ 5-40㎛.

With respect to the roughness, it is preferable to form the surface of the upper layer so as to have the roughness parameters Rz < 5 and / or Rpk < 0.8 mu m in order to further improve its properties.

In a proven way, a DLC layer that does not contain metal-containing and / or metal can be produced by the PA-CVD method.

The present invention also relates to a combination of at least one sliding element and a counter-operative element as described above, and more particularly to a cylinder-or cylinder liner of an internal combustion engine, and more particularly to a spark-ignition engine with a diesel engine or a high- And the relative operating element is iron-based.

According to the present invention, the disclosed coatings show particularly good properties when a Me (C _x N _y ) layer is provided as an intermediate layer between the CrN layer and the DLC layer. Tests using this layered structure indicate that the wear characteristics of the sliding elements, particularly the surfaces of the piston rings, are improved compared to known structures comprising a Cr adhesive layer and a DLC top layer. This can dramatically improve durability. Tests also show that the relative functional coefficients can be drastically reduced.

Figure 1 shows a layer structure according to a preferred exemplary embodiment of the present invention.
2 is a graph showing the relative wear of the piston ring and the cylinder liner.
3 is a graph showing relative friction coefficients of different layer systems.

As shown in FIG. 1, the CrN layer 12 is attached to the base material 10 of the sliding element. The adhesive layer 14 shown in Fig. 1 does not necessarily have to be provided. In particular, this is preferably omitted. In addition, the Me (C _x N _y ) intermediate layer 16 provides the DLC layer 18 with a DLC layer that does not contain the outside metal.

Experiments using this type of structure without the adhesive layer 14 were performed and compared with the comparative example. The table below shows the layer system.

Layer structure
Total layer thickness materials Running surface Adhesive layer
Infrastructure Intermediate layer Top floor [Mu m] DLC series Cr
DLC 3.5 CNDLC01 -
CrN-01 Me (CN) x DLC 8.8 CNDLC02 Cr
CrON-02 Cr DLC 14.5 CNDLC03 Cr
Cr-N-03 Cr DLC 14.6 CNDLC04 Cr
CrON-04 Cr DLC 14.3

Here, the system "DLC series" is a standard DLC layer system without CrN. These layer systems were added to the piston ring and friction kinetic behavior was investigated in combination with an abrasive cast iron cylinder liner in a lubrication environment. Figure 2 shows the relative wear values for the piston ring (at the top) and the cylinder liners. The percentages shown represent the percentage of the original DLC layer remaining after the experiment. If this value is more than 100%, in addition to the DLC layer, the CrN or CrON layer is also at least partially worn. The highest wear value is defined as 100 percent by being used as a reference value for the relative wear of the cylinder liner.

Referring to FIG. 2, the coating according to the present invention with the Me (C _x N _y ) intermediate layer has the lowest relative wear. In the case of cylinder liner abrasion, only known DLC coatings result in lower values. However, wear of the cylinder liners is also an acceptable range for the purposes of the present invention.

A test for the coefficient of friction was also performed and the results are shown in Fig. Here, the example according to the present invention has the lowest relative friction coefficient. Therefore, this requirement also achieves a long service life in addition to a relatively low wear requirement.

12 ... CrN layer 14 ... adhesive layer
16 ... intermediate layer 18 ... DLC layer

Claims (11)

In a sliding element made of cast iron or metal having a coating with a respective inner CrN layer, a middle Me (C _x N _y ) layer, and an outer DLC layer,
The DLC layer comprises a metal-containing substructure layer and a DLC upper layer that does not contain a metal;
The hardness of the CrN layer is 1100-1900 HV 0.002 and / or the hardness of the DLC upper layer not containing the metal is 1700-2900 HV 0.002 and / or the hardness of the metal-containing substructure layer is 800-1600 HV 0.002;
Wherein Me is tungsten, chromium, titanium or silicon, and both x and y are in the range of 0 to 99 atomic%.
delete The method according to claim 1,
Wherein the metal-containing substructure layer and / or the DLC upper layer that does not comprise the metal comprises hydrogen.
The method according to claim 1,
Wherein said metal-containing substructure layer comprises a nanocrystalline metal carbide precipitate.
The method according to claim 1,
The thickness of the CrN layer is 1-30㎛ and / or wherein Me (C _x N _y) the maximum thickness of the layer is 2㎛ and / or thickness of the entire layer is a sliding element, characterized in that 5-40㎛.
The method according to claim 1,
Wherein the DLC upper layer has a roughness Rz < 5 [mu] m and / or Rpk < 0.8 [mu] m.
The method according to claim 1,
Wherein the CrN layer is formed by a metal deposition process and / or the DLC upper layer not comprising the metal-containing substructure layer and / or the metal is formed by PA-CVD.
The method of claim 4,
Wherein the nanocrystalline metal carbide precipitate comprises WC, CrC, SiC, GeC, or TiC.
The method according to any one of claims 1 or 3 to 8,
Characterized in that the sliding element is a piston ring.
The piston ring of claim 9; And
And a cylinder or cylinder liner of the internal combustion engine configured to contact the piston ring.
A sliding element according to any one of claims 1 to 7, And
And an iron-based actuating element in engagement with the sliding element.

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